As described in U.S. Pat. No. 7,374,282 issued May 20, 2008 and U.S. Pat. No. 8,172,393 issued May 8, 2012 a system is shown for providing a pair of sunglasses with a polarized region in the upper portion of the eyeglass lens and a non-polarized region at the bottom of the eyeglass lens so as to permit reading of polarized instruments through the non-polarized region.
In these patents for providing such a gradient polarized pair of sunglasses it is said that the polarizing material is differentially stretched such that at the top region of the sunglasses there is a maximum stretch to provide maximum polarization, whereas at the bottom portion of the sunglass lenses there is little or no stretching, thereby destroying the polarization characteristic of the lens in the lower region of the sunglasses.
It will be appreciated that while such a technique is technically feasible it is somewhat difficult to implement without for instance optical distortion. There is therefore a need to be able to provide an implementation of the gradient polarization sunglasses which is easy to manufacture and which is inexpensive, while at the same time preserving optical quality throughout the extent of the sunglass lenses.
By way of background, for polarized displays such as those in mobile phones, and as illustrated in U.S. Patent Publication No. 2013/0063684, a quarter wave retardation film is applied to a front polarizer on the display device. Glare due to sunlight reflected at the outer surface of the display panel can be reduced by viewing the display through polarized sunglasses and placing this quarter wave plate on the LCD display device results in making the display more visible through the polarized sunglasses.
The destruction of polarization on the polarized displays of handheld mobile devices and other polarized displays is shown in the following U.S. Patent Application Publications, namely 2012/0229732; 2012/0133859; 2012/0069264; 2011/0205471; and 2005/0237440.
All of these systems are utilized to improve the readability of a liquid crystal display in which a polarized film is applied to the display itself. Note that the quarter wave plates or other retarders have not been applied to sunglasses for any purpose much less to be able to read a polarized display in one region of the sunglass while at the same time providing a polarized version of a scene in another portion of the sunglass.
There is therefore a need to be able to implement the manufacture of gradient polarized sunglasses without having to differentially stretch polarization material within the lenses.